Body Mass Index and Decline of Cognitive Function

Abstract

Background: The association between body mass index (BMI) and cognitive function is a public health issue. This study investigated the relationship between obesity and cognitive impairment which was assessed by the Korean version of the Mini-mental state examination (K-MMSE) among mid- and old-aged people in South Korea.

Methods: A cohort of 5,125 adults, age 45 or older with normal cognitive function (K-MMSE≥24) at baseline (2006), was derived from the Korean Longitudinal Study of Aging (KLoSA) 2006~2012. The association between baseline BMI and risk of cognitive impairment was assessed using multiple logistic regression models. We also assessed baseline BMI and change of cognitive function over the 6-year follow-up using multiple linear regressions.

Results: During the follow-up, 358 cases of severe cognitive impairment were identified. Those with baseline BMI≥25 kg/m2 than normal-weight (18.5≤BMI<23 kg/m2) were marginally less likely to experience the development of severe cognitive impairment (adjusted odds ratio [aOR] = 0.73, 95% CI = 0.52 to 1.03; Ptrend = 0.03). This relationship was stronger among female (aOR = 0.63, 95% CI = 0.40 to 1.00; Ptrend = 0.01) and participants with low-normal K-MMSE score (MMSE: 24-26) at baseline (aOR = 0.59, 95% CI = 0.35 to 0.98; Ptrend<0.01). In addition, a slower decline of cognitive function was observed in obese individuals than those with normal weight, especially among women and those with low-normal K-MMSE score at baseline.

Conclusion: In this nationally representative study, we found that obesity was associated with lower risk of cognitive decline among mid- and old-age population.

Fig 1. Schematic diagram of the study population.

Fig 2. Adjusted mean of change of K-MMSE score across baseline body mass index in Korean adults 45+ years.

Abbreviations: K-MMSE, the Korean version of the Mini-mental state examination. Reference category: body mass index 18.5–23 kg/m². * p < .05 ** p < .01, *** p < .001. Change of K-MMSE score was calculated by subtracting 2006 K-MMSE from 2012 K-MMSE. Baseline BMI was measured from the 2006 survey. Age, gender, marital status, health insurance, income, educational level, living place, physical activity, smoking and drinking status, comorbidity, activities of daily livings, depression, and baseline K-MMSE score from the 2006 survey were adjusted for.